Some internal combustion engines include engine control systems that deactivate cylinders under specific low load operating conditions. For example, an eight cylinder engine can be operated using four cylinders to improve fuel economy by reducing pumping losses. This process is generally referred to as displacement on demand or DOD. Operation using all of the engine cylinders is referred to as an activated mode. A deactivated mode refers to operation using less than all of the cylinders of the engine (one or more cylinders not active).
In the deactivated mode, there are fewer firing cylinders. As a result, there is less drive torque available to drive the vehicle driveline and accessories (e.g., alternator, coolant pump, A/C compressor). Engine efficiency, however, is increased as a result of decreased air pumping losses due to the deactivated cylinders not taking in and compressing fresh intake air.
A lifter oil manifold assembly (LOMA) is implemented to activate and deactivate select cylinders of the engine. The LOMA includes a series of lifters and solenoids associated with corresponding cylinders. The solenoids are selectively energized to enable hydraulic fluid flow to the lifters to inhibit valve lifter operation, thereby deactivating the corresponding cylinders. The solenoids remain energized while the engine operates in the deactivated mode. As a result, electrical current to the solenoids must be maintained throughout operation in the deactivated mode. The current supply to the solenoids during the deactivated mode increases the vehicle's current requirements and solenoid operating temperatures.